Direct current to direct current (DCDC) converter with multiple DC-DC conversion modules and control method thereof

1 . A Direct Current to Direct Current (DCDC) converter, comprising a plurality of DCDC conversion modules and a controller, wherein:

each of the DCDC conversion modules comprises two bidirectional isolated DCDC units connected in parallel, each of the two bidirectional isolated DCDC units comprises a resonant circuit and a non-isolated buck/boost circuit connected in cascade; wherein a frequency of each of the resonant circuits is fixed for achieving voltage isolation of each resonant circuit; and the plurality of DCDC conversion modules are connected in parallel for improving power efficiency of the Direct Current to Direct Current converter;

the controller is electrically connected to each of the two bidirectional isolated DCDC units, and is configured to control current sharing among each of the non-isolated buck/boost circuits;

wherein each resonant circuit comprises an LLC extension circuit;

wherein the LLC extension circuit comprises a first three-phase circuit, a second three-phase circuit and three transformers, wherein:

the first three-phase circuit is connected to primary sides of the three transformers, and the second three-phase circuit is connected to secondary sides of the three transformers;

wherein each non-isolated buck/boost circuit adopts an interleaving buck/boost circuit;

wherein each non-isolated buck/boost circuit comprises a first branch, a second branch, a seventh inductor and an eighth inductor, wherein:

the first branch and the second branch are connected in parallel, the first branch comprises a thirteenth switch tube and a fourteenth switch tube connected in series, and the second branch comprises a fifteenth switch tube and a sixteenth switch tube connected in series: a first end of the seventh inductor is connected to a second end of the fifteenth switch tube and a first end of the sixteenth switch tube, a first end of the eighth inductor is connected to a second end of the thirteenth switch tube and a first end of the fourteenth switch tube, and a second end of the seventh inductor is connected to a second end of the eighth inductor.

2 . The Direct Current to Direct Current (DCDC) converter according to claim 1 , wherein the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor and a third capacitor; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of the first inductor is connected between the first switch tube and the second switch tube, a first end of the second inductor is connected between the third switch tube and the fourth switch tube, and a first end of the third inductor is connected between the fifth switch tube and the sixth switch tube; a second end of the first inductor is connected to a first end of a primary side of a first transformer of the three transformers, a second end of the primary side of the first transformer is connected to a first end of the first capacitor, a second end of the second inductor is connected to a first end of a primary side of a second transformer of the three transformers, a second end of the primary side of the second transformer is connected to a first end of the second capacitor, a second end of the third inductor is connected to a first end of a primary side of a third transformer of the three transformers, a second end of the primary side of the third transformer is connected to a first end of the third capacitor, and a second end of the first capacitor and a second end of the second capacitor are connected to a second end of the third capacitor; or

the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first capacitor, a second capacitor and a third capacitor; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of a primary side of a first transformer of the three transformers is connected between the first switch tube and the second switch tube, a first end of a primary side of a second transformer of the three transformers is connected between the third switch tube and the fourth switch tube, and a first end of a primary side of a third transformer of the three transformers is connected between the fifth switch tube and the sixth switch tube; a second end of the primary side of the first transformer is connected to a first end of the first capacitor, a second end of the primary side of the second transformer is connected to a first end of the second capacitor, a second end of the primary side of the third transformer is connected to a first end of the third capacitor, and a second end of the first capacitor and a second end of the second capacitor are connected to a second end of the third capacitor; or

the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first inductor, a second inductor and a third inductor; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of the first inductor is connected between the first switch tube and the second switch tube, a first end of the second inductor is connected between the third switch tube and the fourth switch tube, and a first end of the third inductor is connected between the fifth switch tube and the sixth switch tube; a second end of the first inductor is connected to a first end of a primary side of a first transformer of the three transformers, a second end of the second inductor is connected to a first end of a primary side of a second transformer of the three transformers, and a second end of the third inductor is connected to a first end of a primary side of a third transformer of the three transformers; a second end of the primary side of the first transformer and a second end of the primary side of the second transformer are connected to a second end of the primary side of the third transformer; or,

the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of a primary side of a first transformer of the three transformers is connected between the first switch tube and the second switch tube, a first end of a primary side of a second transformer of the three transformers is connected between the third switch tube and the fourth switch tube, and a first end of a primary side of a third transformer of the three transformers is connected between the fifth switch tube and the sixth switch tube; a second end of the primary side of the first transformer and a second end of the primary side of the second transformer are connected to a second end of the primary side of the third transformer.

3 . The Direct Current to Direct Current (DCDC) converter according to claim 1 , wherein the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fourth inductor, a fifth inductor, a sixth inductor, a fourth capacitor, a fifth capacitor and a sixth capacitor; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected to a first end of the fourth inductor, and a second end of the fourth inductor is connected between the seventh switch tube and the eighth switch tube; a first end of a secondary side of a second transformer of the three transformers is connected to a first end of the fifth inductor, and a second end of the fifth inductor is connected between the ninth switch tube and the tenth switch tube; a first end of a secondary side of a third transformer of the three transformers is connected to a first end of the sixth inductor, and a second end of the sixth inductor is connected between the eleventh switch tube and the twelfth switch tube; a second end of the secondary side of the first transformer is connected to a first end of the fourth capacitor, a second end of the secondary side of the second transformer is connected to a first end of the fifth capacitor, a second end of the secondary side of the third transformer is connected to a first end of the sixth capacitor, and a second end of the fourth capacitor and a second end of the fifth capacitor are connected to a second end of the sixth capacitor; or

the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fourth capacitor, a fifth capacitor and a sixth capacitor; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected between the seventh switch tube and the eighth switch tube; a first end of a secondary side of a second transformer of the three transformers is connected between the ninth switch tube and the tenth switch tube; a first end of a secondary side of a third transformer of the three transformers is connected between the eleventh switch tube and the twelfth switch tube; a second end of the secondary side of the first transformer is connected to a first end of the fourth capacitor, a second end of the secondary side of the second transformer is connected to a first end of the fifth capacitor, a second end of the secondary side of the third transformer is connected to a first end of the sixth capacitor, and a second end of the fourth capacitor and a second end of the fifth capacitor are connected to a second end of the sixth capacitor; or

the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fourth inductor, a fifth inductor and a sixth inductor; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected to a first end of the fourth inductor, and a second end of the fourth inductor is connected between the seventh switch tube and the eighth switch tube; a first end of a secondary side of a second transformer of the three transformers is connected to a first end of the fifth inductor, and a second end of the fifth inductor is connected between the ninth switch tube and the tenth switch tube; a first end of a secondary side of a third transformer of the three transformers is connected to a first end of the sixth inductor, and a second end of the sixth inductor is connected between the eleventh switch tube and the twelfth switch tube; a second end of the secondary side of the first transformer and a second end of the secondary side of the second transformer are connected to a second end of the secondary side of the third transformer; or,

the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube and a twelfth switch tube; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected between the seventh switch tube and the eighth switch tube, a first end of a secondary side of a second transformer of the three transformers is connected between the ninth switch tube and the tenth switch tube, a first end of a secondary side of a third transformer of the three transformers is connected between the eleventh switch tube and the twelfth switch tube, and a second end of the secondary side of the first transformer and a second end of the secondary side of the second transformer are connected to a second end of the secondary side of the third transformer.

4 . A control method of the Direct Current to Direct Current (DCDC)-converter according to claim 1 , comprising:

during an operation in a first direction, controlling driving of two resonant circuits comprised in each of the DCDC conversion modules at corresponding positions to be opposite, and controlling the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units to work in a buck state and causing output current of the respective non-isolated buck/boost circuits to be equal; and

during an operation in a second direction, controlling driving of two resonant circuits comprised in each of the DCDC conversion modules at corresponding positions to be opposite, and controlling the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units to work in a DC boost state and causing output current of the respective non-isolated buck/boost circuits to be equal, wherein the first direction is opposite to the second direction.

5 . The method according to claim 4 , wherein controlling the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units to work in the buck state and causing output current of the respective non-isolated buck/boost circuits to be equal comprises:

generating a first current reference value according to a preset voltage reference value and an output voltage sampling value, and adjusting a duty ratio of the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units according to the first current reference value and an output current sampling value of the respective non-isolated buck/boost circuits, so as to cause the output current of each of the non-isolated buck/boost circuits to be equal.

6 . The method according to claim 4 , wherein controlling the non-isolated buck/boost circuits included in each of the two bidirectional isolated DCDC units to work in the DC boost state and causing output current of the respective non-isolated buck/boost circuits to be equal comprises:

controlling the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units to generate an intermediate bus voltage of each of the bidirectional isolated DCDC units, and obtaining a second current reference value according to an intermediate bus voltage reference value and an intermediate bus voltage sampling value of each of the two bidirectional isolated DCDC units; and

adjusting a duty ratio of the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units according to the second current reference value and an input current sampling value of the non-isolated buck/boost circuit included in each of the two bidirectional isolated DCDC units, so as to cause input current of the respective non-isolated buck/boost circuits to be equal.

7 . A bidirectional charging and discharging device, comprising a Direct Current to Direct Current (DCDC) converter, wherein:

the Direct Current to Direct Current (DCDC) converter comprises a plurality of DCDC conversion modules and a controller;

each of the DCDC conversion modules comprises two bidirectional isolated DCDC units connected in parallel, each of the two bidirectional isolated DCDC units comprises a resonant circuit and a non-isolated buck/boost circuit connected in cascade; wherein a frequency of each of the resonant circuits is fixed for achieving voltage isolation of each resonant circuit; and the plurality of DCDC conversion modules are connected in parallel for improving power efficiency of the Direct Current to Direct Current converter;

the controller is electrically connected to each of the two bidirectional isolated DCDC units, and is configured to control current sharing among the non-isolated buck/boost circuits;

wherein each resonant circuit comprises an LLC extension circuit;

wherein the LLC extension circuit comprises a first three-phase circuit, a second three-phase circuit and three transformers, wherein:

the first three-phase circuit is connected to primary sides of the three transformers, and the second three-phase circuit is connected to secondary sides of the three transformers:

wherein each non-isolated buck/boost circuit adopts an interleaving buck/boost circuit;

wherein each non-isolated buck/boost circuit comprises a first branch, a second branch, a seventh inductor and an eighth inductor, wherein:

the first branch and the second branch are connected in parallel, the first branch comprises a thirteenth switch tube and a fourteenth switch tube connected in series, and the second branch comprises a fifteenth switch tube and a sixteenth switch tube connected in series; a first end of the seventh inductor is connected to a second end of the fifteenth switch tube and a first end of the sixteenth switch tube, a first end of the eighth inductor is connected to a second end of the thirteenth switch tube and a first end of the fourteenth switch tube, and a second end of the seventh inductor is connected to a second end of the eighth inductor.

8 . The bidirectional charging and discharging device, according to claim 7 , wherein the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor and a third capacitor; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of the first inductor is connected between the first switch tube and the second switch tube, a first end of the second inductor is connected between the third switch tube and the fourth switch tube, and a first end of the third inductor is connected between the fifth switch tube and the sixth switch tube; a second end of the first inductor is connected to a first end of a primary side of a first transformer of the three transformers, a second end of the primary side of the first transformer is connected to a first end of the first capacitor, a second end of the second inductor is connected to a first end of a primary side of a second transformer of the three transformers, a second end of the primary side of the second transformer is connected to a first end of the second capacitor, a second end of the third inductor is connected to a first end of a primary side of a third transformer of the three transformers, a second end of the primary side of the third transformer is connected to a first end of the third capacitor, and a second end of the first capacitor and a second end of the second capacitor are connected to a second end of the third capacitor; or

the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first capacitor, a second capacitor and a third capacitor; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of a primary side of a first transformer of the three transformers is connected between the first switch tube and the second switch tube, a first end of a primary side of a second transformer of the three transformers is connected between the third switch tube and the fourth switch tube, and a first end of a primary side of a third transformer of the three transformers is connected between the fifth switch tube and the sixth switch tube; a second end of the primary side of the first transformer is connected to a first end of the first capacitor, a second end of the primary side of the second transformer is connected to a first end of the second capacitor, a second end of the primary side of the third transformer is connected to a first end of the third capacitor, and a second end of the first capacitor and a second end of the second capacitor are connected to a second end of the third capacitor; or

the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first inductor, a second inductor and a third inductor; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of the first inductor is connected between the first switch tube and the second switch tube, a first end of the second inductor is connected between the third switch tube and the fourth switch tube, and a first end of the third inductor is connected between the fifth switch tube and the sixth switch tube; a second end of the first inductor is connected to a first end of a primary side of a first transformer of the three transformers, a second end of the second inductor is connected to a first end of a primary side of a second transformer of the three transformers, and a second end of the third inductor is connected to a first end of a primary side of a third transformer of the three transformers; a second end of the primary side of the first transformer and a second end of the primary side of the second transformer are connected to a second end of the primary side of the third transformer; or,

the first three-phase circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube; the first switch tube and the second switch tube are connected in series, the third switch tube and the fourth switch tube are connected in series, and the fifth switch tube and the sixth switch tube are connected in series; a first end of a primary side of a first transformer of the three transformers is connected between the first switch tube and the second switch tube, a first end of a primary side of a second transformer of the three transformers is connected between the third switch tube and the fourth switch tube, and a first end of a primary side of a third transformer of the three transformers is connected between the fifth switch tube and the sixth switch tube; a second end of the primary side of the first transformer and a second end of the primary side of the second transformer are connected to a second end of the primary side of the third transformer.

9 . The bidirectional charging and discharging device, according to claim 7 , wherein the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fourth inductor, a fifth inductor, a sixth inductor, a fourth capacitor, a fifth capacitor and a sixth capacitor; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected to a first end of the fourth inductor, and a second end of the fourth inductor is connected between the seventh switch tube and the eighth switch tube; a first end of a secondary side of a second transformer of the three transformers is connected to a first end of the fifth inductor, and a second end of the fifth inductor is connected between the ninth switch tube and the tenth switch tube; a first end of a secondary side of a third transformer of the three transformers is connected to a first end of the sixth inductor, and a second end of the sixth inductor is connected between the eleventh switch tube and the twelfth switch tube; a second end of the secondary side of the first transformer is connected to a first end of the fourth capacitor, a second end of the secondary side of the second transformer is connected to a first end of the fifth capacitor, a second end of the secondary side of the third transformer is connected to a first end of the sixth capacitor, and a second end of the fourth capacitor and a second end of the fifth capacitor are connected to a second end of the sixth capacitor; or

the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fourth capacitor, a fifth capacitor and a sixth capacitor, the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected between the seventh switch tube and the eighth switch tube; a first end of a secondary side of a second transformer of the three transformers is connected between the ninth switch tube and the tenth switch tube; a first end of a secondary side of a third transformer of the three transformers is connected between the eleventh switch tube and the twelfth switch tube; a second end of the secondary side of the first transformer is connected to a first end of the fourth capacitor, a second end of the secondary side of the second transformer is connected to a first end of the fifth capacitor, a second end of the secondary side of the third transformer is connected to a first end of the sixth capacitor, and a second end of the fourth capacitor and a second end of the fifth capacitor are connected to a second end of the sixth capacitor; or

the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a fourth inductor, a fifth inductor and a sixth inductor; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected to a first end of the fourth inductor, and a second end of the fourth inductor is connected between the seventh switch tube and the eighth switch tube; a first end of a secondary side of a second transformer of the three transformers is connected to a first end of the fifth inductor, and a second end of the fifth inductor is connected between the ninth switch tube and the tenth switch tube; a first end of a secondary side of a third transformer of the three transformers is connected to a first end of the sixth inductor, and a second end of the sixth inductor is connected between the eleventh switch tube and the twelfth switch tube; a second end of the secondary side of the first transformer and a second end of the secondary side of the second transformer are connected to a second end of the secondary side of the third transformer; or,

the second three-phase circuit comprises a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube and a twelfth switch tube; the seventh switch tube and the eighth switch tube are connected in series, the ninth switch tube and the tenth switch tube are connected in series, and the eleventh switch tube and the twelfth switch tube are connected in series; a first end of a secondary side of a first transformer of the three transformers is connected between the seventh switch tube and the eighth switch tube, a first end of a secondary side of a second transformer of the three transformers is connected between the ninth switch tube and the tenth switch tube, a first end of a secondary side of a third transformer of the three transformers is connected between the eleventh switch tube and the twelfth switch tube, and a second end of the secondary side of the first transformer and a second end of the secondary side of the second transformer are connected to a second end of the secondary side of the third transformer.